This error in Zimbra Talk happens since I upgraded my ZCS to 8.7.6 version.I followed your recomendation in other thread of this forum, but the problem continues:

"After the Zimbra-upgrade has been completed, you have perform these steps on the Zimbra installation.Reinstall zmpkg and the previously installed zimletsDownload latest zmpkg-installerIn case of Zimbra 8.7, you need at least the zmpkg-installer in version 1.4.4.2, wich you will get here:

zm-apt* commands are not supposed to be run as root - only as zimbra user.

However -to track down the issue you are facing it would be good to see where it fails. The actual failure is that something that is supposed to return JSON does not. Ususally this also means that the HTTP status code is not 200. If you are using chrome, open the developer tools and open the network tab, then reload zimbra webclient. Check for requests that are displayed in red and provide them here.

In addition and just by accident: Do you use virtual hosts in zimbra? If yes, you have to apply the proxy customization to /opt/zimbra/conf/nginx/templates/nginx.conf.web.https.default.template and /opt/zimbra/conf/nginx/templates/nginx.conf.web.https.template in order to make it work.

I applyied the proxy customization to /opt/zimbra/conf/nginx/templates/nginx.conf.web.https.default.template and /opt/zimbra/conf/nginx/templates/nginx.conf.web.https.template and then run /opt/zimbra/libexec/zmproxyconfgen but I get a new error in the admin console when open the Zimbra Talk zimlet configuration :

are you sure that you correctly re-installed zmpkg and all packages? In order to make sure that is the case, please follow these steps:1. as root re-install zmpkg (zimbra upgrade will have changed some file permission that make zmpkg/zm-apt-get fail afterwards)2. as zimbra-user run zm-apt-get dist-upgrade (this may update some packages)3. since you attempted uninstall: zm-apt-get install zcs-vnc-talk4. make sure that each package is reinstalled (the zimbra upgrade chages some files and permissions, but zm-apt database can not be aware of this; the recommended way is to let zm-apt-get reinstall the packages): zm-apt-get install --reinstall `zmpkg list | grep -v zmpkg | grep "^ii" | awk '{print $2}' | tr '\n' ' '`5. as odd as it may seem, but we have seen zimbra sometimes not bundling all javascript components correctly - restart zimbra server

Then clear browser cache (zimbra mailboxd delivers web client bundle with long cache validity, but we want to make sure to actually load it from server again). Admitted - this looks like quite a lot of effort. But after that everything should work fine.